Method of erecting floating roofs and apparatus therefor



Aug. 19, 1958 J. F. MUMMERT ET AL METHOD OF ERECTING FLOATING ROOFS ANDAPPARATUS THEREFOR 3 Sheets-Sheet 1 Filed March 8, 1954 Allg- 1958 J. F.MUMMERT ET AL 2,847,755

METHOD OF ERECTING FLOATING ROOFS AND APPARATUS THEREFOR Filed March 8,1954 3 Sheets-Sheet 2 I 23 7 ii x I 1/11/- A] I jwuc/nfomq JOHN EMUMMERT BART MILL/17M? ROBERT L. BROWN Aug. 19, 1958 UMMER F. M T ET ALMETHOD OF ERECTING FLOATING ROOF'S AND APPARATUS THEREFOR Filed March 8,1954 3 Sheets-Sheet 3 gwuoryto m JOHN F MUMMERT 5,427 MAL/HMS R050??- LBR United States Patent Ofitice 2,847,755 Patented Aug. 19, 1958 METHODOF ERECTHNG FLOATING ROOFS AND APPARATUS THEREFOR John F. Mummert, BartWilliams, and Robert L. Brown; Birmingham, Ala., assignors to ChicagoBridge & iron Company, a corporation of Illinois Application March 8,1954, Serial No. 414,778 9 Claims. (Cl. 29-429) This invention relatesto liquid storage tanks having floating roofs and more particularly tothe method and apparatus used in connection with the construction of thefloatingroof in a field-erected liquid storage tank.

Crude oil, gasoline and other similar products as well as chemicals areoften stored in quite large storage tanks which are erected out in thefield. One fairly standard size of tank has a capacity of 80,000barrels. With volatile products, there is the problem of loss due toevaporation and the problem of fire. For some years past, large storagetanks have been equipped with a floating cover generally referred to asa floating roof. Floating roofs as used in liquidstorage tanks generallytake on one of three basic forms. The simplest form is referred .to as apan-type roof and is similar to a pie pan in that it has a generallysingle thickness of plate deck joined at its peripheryto an upstandingrim which provides the freeboard for the roof as it floats in theliquid. Another yPe of roof is one having part of its covering surfaceof single plate deck joined, however, to pontoons which provide thebuoyancy. A third type of roof is one referred to .as a double-deck roofin that it has a bottom Plate deck and an upper plate deck which isspaced above the bottom deck. These decks are joined in appropriatemanner so that they act in unison.

Floating roof tanks ordinarily have no weather cover or roof so thatrain and snow can fall directly on the floating roof even when the roofis down near the bottom of the tank. This water must be drained eitherthrough the product or through appropriate pipes or hoses to theoutside. These appurtenances are placed under the float ing roof betweenthe roof and the bottom of the tank. Other appurtenances are likewisesituated in the bottom of the tank so that the roof itself cannotordinarily be allowed to rest directly on the bottom when the tank isempty. The usual procedure is to provide the roof with a number ofsupporting posts which land the roof on the bottom of the tank but at anelevation above the bottom. This leaves room for all of theappurtenances that are usually placed in the tank bottom and insuresthat no damage will be done to them when the tank is emptied.

Construction procedure in the past has generally been to build thefloating roof within the tank at its proper low service position. Thisposition is perhaps three feet or a little more above the bottom of thetank and may vary considerably. The roofs are built of plate metalgenerally shaped in the shop and shipped to the site in flat condition.These plates have to be supported during the construction so that thewelders may join them together to form the complete floating roofstructure. The practice has been to use a considerable amount oftemporary support Within the tank itself to support the roof plates atlow service elevation and to remove this material through a manhole inthe side of the tank after the roof has been completed and placed on itsown roof supports. The procedure is expensive in both material and laborand adds considerably to the construction time necessary,

the bottom of the tank 2 which is a factor in the cost of the tank andfloating roof structure itself.

The present invention presents a method of construction in which notemporary framing is required in certain instances and a very smallamount of rather lightweight and easily handled framing is necessary inother instances. Ordinarily, the roof is constructed on the bottom ofthe tank itself and only suflicient framing is used to achieve theproper slope of the roof plates. Should have a slope corresponding tothe slope desired in the bottom deck of the floating roof, the roof maybe constructed directly on the tank bottom. in the past, there have beensuggestions that such construction procedure would be desirable. Therehas been, however, the difliculty of getting the roof to its properposition after it is constructed on the tank bottom. It has beensuggested that the roof should be floated but the shape of the roof whenfloating may be considerably different from its shape when supported onits post supports. A floating roof must have the proper drainagecharacteristics in order to withstand the climatic conditions underwhich it may be used. It is thus exceedingly important that the roofdecks have a proper pitch and that the structure be made in such a wayas to maintain that pitch when the tank is empty and when the roof isfloating on the stored product.

The present invention also apparatus for elevating the roof to itsproper low service position and permitting securing the roof in thatposition. Once the tank is placed in service and the roof floated 0n theproduct, the tank may be emptied and the roof will return to land on itspost supports in the low service position.

The invention will be illustrated and described in connection with theaccompanying drawings in which:

Figure l is a small scale vertical section taken through a liquidstorage tank and a floating roof therein ready to be elevated to its lowservice position;

Figure 2 is similar to Figure 1 and shows the roof raised to its properlow service position;

Figure 3 is similar to Figure 1 and illustrates a roof of the pontoontype;

Figure 4 is an enlarged fragmentary vertical sectional view takenthrough the tank and a portion of the roof showing one of the postsupports for the roof;

Figure 5 is a fragmentary vertical sectional view through the tank andpart of the roof showing the raising device in position in a floatingroof which has been constructed directly on the bottom of the tank;

Figure 6 is a view similar to Figure 5 showing the provides a method androof after it has been elevated and fixed in low service position;

Figure 7 is a front elevation View of the hoisting mechanism;

Fig. 8 is a side elevational trated in Figure 7;

Figure 9 is a fragmentary vertical sectional view through a section of afloating roof showing the sleeve member associated with the hoistingmechanism;

Figure 10 is an enlarged fragmentary sectional view through the upperend of the hoisting mechanism showing the top bearing support;

Figure 11 is a bottom plan view of the bearing member used with thehoisting mechanism;

Figure 12 is a fragmentary plan view toward the bottom of a tank showingtemporary framing used in constructing a pontoon type floating roof; and

Figure 13 is a fragmentary vertical sectional view through a tankshowing the temporary framing illustrated in Figure 12 with the pontoontype roof partially completed thereon.

The floating roof storage tanks are made in a variety view of themechanism illusof sizes and the capacities, of course, depend upon thediameter and height of the tank. By way of example, a tank 120 ft. indiameter by 48 ft. high would have a capacity of about 96,000 barrels.

The tanks are constructed with a bottom of plates joined to side wallplates 11 reinforced at the top by a wind girder 12 and provided with.inlet and outlet pipe connections 13. The tank is built on a preparedfoundation which may include a concrete ring wall under the shell 11 ofthe tank and is ordinarily constructed on a sand base. The bottom plates10 may often be given a slope from the shell of the tank upwardly towarda center in order that water might drain through the product to theoutside rim of the tank. Tanks generally are of welded construction withthe bottom plates being lap welded and the shells of the tanks beingbutt welded both on the horizontal and vertical joints. The innersurface of the tank sidewalls are generally smooth and any offset due toa difference in size of the courses of the plates being taken up on theoutside of the tank rather than on the inside. This permits a fairlysmooth surface for a sealing ring to slide upon with movement of thefloating roof up and down within the tank.

In Figures 1 and 2, a floating roof is illustrated after completion inthe tank bottom and in Fig. 2 it is elevated to the low position it willoccupy during service. The roof is of the double-deck type. That is, ithas a lower deck of plates 14 and an upper deck 15 enclosing anintervening space. The roof is built in annular sections for the mostpart, the outermost section 16 being untrussed whereas intermediatesection 17 may be provided with trusses extending radially in the roof.It is generally known that the tanks and roofs are round, orsubstantially so, so that no illustration of the tank or roof in thisregard has been made.

The procedure followed in erecting a floating roof structure of thedouble-deck type in accordance with the present invention permits theconstruction of the roof directly on the bottom. It will be noted inFigure 1 that the bottom of the tank has substantially the same slope asthe bottom deck 14 of the floating roof. The first step in theconstruction is the placement of bottom deck sketch plates 18 which arethose plates at the peripheral edge of the bottom deck next to the shellof the tank. Care is exercised to secure the proper placing of thesketch plates to insure that the plates form a true circle. If the shellof the tank is no more than A; inch out of round, templates may be usedplaced against the shell to locate the sketch plates 18. When thesesketch plates have been welded together, a sealing ring is installed onthe tank shell to be later attached to the roof for movement with it asit floats upon the stored product. This sealing ring forms no part ofthe present invention and therefore has not been illustrated.

Prior to, or simultaneously with, the placing of the sketch plates, asmall pad plate is placed on and welded to the bottom of the tankwhenever a roof support will bear on the bottom. In Figure 4, a pad 19is illustrated as welded to the bottom 10 of the tank, and is generallya square or round plate larger than the post which will 4' bear againstit.

The outer rim 20 of the floating roof is next attached to the sketchplates, care being exercised to insure that the rim is plumb. Theconstruction of the other parts of the roof then proceeds until the roofis finished as far as its bottom deck and bulkheads 21 and 22. areconcerned. Before the upper deck 15 is placed in position, sleevemembers 23, having a barrel 24 and a pedestal 25, are welded in positionover openings in the lower deck. Care is taken to make sure that thebarrel of the sleeve member is substantially vertically aligned and ashear plate 26 is inserted between the outer rim or bulkhead and thesleeve. The shear plate is welded to both to insure that the sleeveremains vertical. The position of these sleeves is chosen to be in theexact spot for a permanent roof 4 support. Ordinarily, the sleeves arepositioned in a ring about the tank with the inner ring of supportsconcentric within the outer rings.

The roof is then completed by the installation of the upper deck 15.Holes 27 are burned in the upper deck over the sleeve member 23 so thatthe sleeve member will be accessible in raising the roof to itspermanent low position. Each sleeve member is provided with a pair ofapertured lugs 28 on diametrically opposite sides by which a jackingmechanism may be attached to raised the roof.

Following the completion of the roof to the extent set out above, a jackmember is applied to eachsleeve 23 in the roof for the purpose ofraising the roof as a unit.

I The jack members utilize a pair of tension straps 29 having abifurcated lug 30 at the lower end for fitting it over the apertured lug28 on the sleeve member. A bolt 31 may be inserted to secure themtogether. A lug member 32 joins the upper ends of the tension straps andis more particularly set out in Figure 10. In this is a thrust bearing33 against which a screw member 34 may thrust upward. This screw memberhas a thread 35 particularly adapted to bear considerable load. The top36 of the screw is shaped so as to receive a turning crank.

To raise the roof, a supporting post 37 is inserted through the sleevemember. This post is hollow and may be a tube or pipe. A hearing lug 38threadedly engaging screw 34 is provided with an annular groove 39 tofit over the top of the post 37. Ears 40 fit about the tension straps 29to guide the lug in its vertical travel. It may thus be seen that theturning of the screw 34 may travel the bearing lug 38 downwardly movingthe post 37 through the sleeve and drawing the roof upwardly. In orderthat allparts of the roof be acting in unison, a scale 41 is provided onone of the tension straps so that the workmen may gauge the movement ofthe roof upwardly. The scales shown indicate movements from 1 inch to 42inches. The procedure followed is to place a slight bit of tension oneach jack and then sufficient men to man the jacks in unison to raisethe roof under the direction of one person so that all parts of therooof are raised in equal increments. A roof, even though weighingseveral hundred thousand pounds, may thus easily be raised into properposition.

When the roof has reached its upper position, a weld 42 is appliedbetween the posts 37 and sleeve 23 to secure them together. The jack isremoved and the shear plate 26 is also welded to the post 37.Thereafter, the roof upon approaching the bottom will land on the postsand be held in its low position as illustrated in Figures 2 and 6. Insome instances, it may be desirable to raise the roof to an even higherposition. In such cases, an additional pipe 43 may be telescoped insidethe post 37 and the lifting procedure repeated to raise the roof untilan opening 44 reaches an opening 45 in the post 37 to receive a pin. Alifting ring 46 is applied to the top of the post after removal of thejack mechanism.

In the construction of some roofs, the bottom of the tank may not havethe proper shape for the bottom of the roof. Figures 3, 12, and 13illustrate one type of roof which has a bottom slope different from thatof the bottom of the tank. In this instance, a pontoon type roof has acentral single plate thickness deck 50 and an outer annular pontoon 51.The bottom plates 52 of the pontoon slope upwardly while the upperplates 53 have a slight downward pitch toward the center of the roof inorder to drain water toward the center. The construction procedure withsuch a roof varies from the procedure outlined above only in the initialsteps. Sufficient temporary framing is used to support the bottom of theroof in its proper shape. The outer peripheral slope of the pontoonbottom deck 52 may be provided by radially aligned rods 54 temporarilysupported by short posts 55 asanrse and at their inner end by an angleiron 56 supported above the deck by small hangers 57. The central singledeck portion 50 may be supported on 2 by 6 boards 58 supported in placeby blocks of wood 59. Only a sutficient number of these boards need beplaced in the tank to support the plates themselves which may be of theorder of 18 ft. long and '5 or 6 ft. wide. The procedure for placing thebottom deck and the rim 60 of the roof is substantially the same asdescribed above. The sketch plates 61 are first placed in position andthen joined to other plates 62 which form the bottom of the pontoon andcontinue on to form the single deck 50. The inner rim 63 of the pontoonis placed in proper position after the initial sleeves 23 are fixed inthe pontoon.

It is ordinarily only necessary to lift a pontoon-type roof to itsproper position by root supports in the outer and next inner ring ofsupports. A double-deck roof is generally lifted over its entire area.On the larger sizes of single deck pan-type roofs or pontoon-type roofs,some lifting will also be carried on in the single deck area to preventtoo much sagging in the plates.

It will be noted in Figure 4 that the roof support takes onsubstantially the same appearance after the jack is removed as such roofsupports have in ordinary types of construction. The opening 27 whichwas cut in the top deck may be closed by cover plate 27a and the sleeve23 initially placed in the roof is left in the roof although itsfunction has generally ceased to exist after the jacking operation. Theroof sleeves are welded securely in position so that any movementthereafter cannot occur. The roof is not only economically constructedbut is raised to its proper position in a very easy and quick mannermaintaining the proper slope of the roof when landed and not floating.Ordinarily suflicient manholes are provided in the roof to permitworkmen to enter the space between the roof and tank bottom to placesuch appurtenances as are necessary in the tank and under the roof. Atthe same time, the men can check the elevation of all of the roofsupports and in the event that the bottom of the tank has settled,compensation can be made at that time so that the correct slope of theroof is obtained when in its elevated position.

The foregoing detailed description has been given for cleamess ofunderstanding only, and no unnecessary limitations should be understoodtherefrom, for some modifications will be obvious to those skilled inthe art.

We claim:

1. The method of constructing a floating roof in a field erected liquidstorage tank which comprises, temporarily supporting all roof parts inthe tank from the tank bottom and on blocking in areas where roof andtank bottom configuration difler, securing the roof parts together tosubstantially complete the roof in the tank in its temporarily supportedposition, placing upright roof supporting posts in the roof so as tobear downwardly on the tank bottom, then jacking the substantiallycompleted roof from a plurality of points as a unit over said posts toproper low service position in the tank and securing the roof to theposts to thereafter limit downward travel of the roof in the tank to thelow service position supported on said posts.

2. The method as specified in claim 1 wherein the peripheral portion ofthe floating roof is placed in direct contact with the tank bottomplates and the central portion of the roof is placed on shallowtemporary framing to give the bottom of the roof a configurationdifferent from that of the tank bottom.

3. The method of constructing a floating roof for a field erectedstorage tank, which comprises placing roof parts on the tank bottom inproper position to be welded into a substantially complete floatingroof, securing the parts together, inserting roof support posts throughthe roof to bear on the tank bottom and then lifting the roof to properposition above the tank bottom by jacking the roof as a unit upwardlyover said support posts.

4. The method of constructing a floating roof for a field erectedstorage tank, which comprises welding together roof parts properlypositioned in the bottom of the tank to substantially complete thefloating structure of the roof, supporting the roof parts during weldingon the tankbottom so that the substantially completed roof is below itsintended low service position, and then lifting the roof to low serviceposition as a unit by jacking against roof support posts extendingthrough the roof and bearing against the tank bottom.

5. The method of constructing a floating roof for a field erected liquidstorage tank which comprises, fitting together preshaped plates to formthe roof structure on the bottom of the tank, placing auxiliary sleeveswithin the roof over predetermined tank bottom areas, telescoping usualroof support members through the sleeves to bear against the tankbottom, raising the roof as a body by jacking said roof support membersthrough the sleeves and then securing the sleeves and roof supportmembers together to hold the roof in its proper elevated position abovethe tank bottom.

6. The method of constructing a floating roof for a liquid storage tankwhich comprises, securing roof support pads in predetermined locationson the tank bottom, locating roof bottom deck sketch plates relative tothe tank shell to form the peripheral portion of the roof deck restingon the bottom of the tank, welding the positioned sketch plates tobottom deck plates also placed on the tank bottom, securing an outerroof rim plate in upstanding position to the bottom deck sketch platesand roof bulkheads to the bottom plates and rim plate, forming openingsin the bottom deck over said support pads and securing sleeve members tothe bottom deck over the openings, welding top deck plates to thebulkheads and rim plate substantially to complete the floating roof,inserting pipe support members through the sleeve members so as to bearagainst the support pads and extend above the roof, mounting weightlifting jacks on the pipe supports and sleeves, operating all of thejacks together to raise the roof from the bottom of the tank to finalposition, then Welding the pipe supports and sleeve members together tomaintain the roof in elevated position and then removing the jacks.

7. The method as specified in Claim 3 in which the roof is raisedprogressively by jacking on a plurality of spaced roof supports in theform of posts and securing the roof to the posts in permanent fashionafter raising the roof to proper elevation in the tank.

8. Apparatus for raising a newly constructed floating roof from thebottom of a liquid storage tank to proper low service position above thebottom, comprising: a sleeve member having a barrel and a pedestaladapted to be secured to the roof so that the barrel extends substantially vertically over an opening in the deck of the roof; a pair ofapertured lugs on opposite sides of the upper portion of the barrel; apost member telescoped through the sleeve member and extendingdownwardly to contact the bottom of the tank and upwardly to exposeportion above the floating roof; a jack member including a bearing nutadapted to rest on top of the post member and threadedly receiving a rodextending downwardly within the post member; a pair of tension strapseach secured to one of said apertured lugs and to the top of saidthreaded rod so that turning of the rod may force the post memberdownwardly through the sleeve to elevate the roof from bearing on thebottom of the tank to being supported on the post.

9. Apparatus for raising a new constructed floating roof from the bottomof a liquid storage tank to proper low service position above thebottom, comprising: a sleeve member secured to the roof and having acentral passage extending substantially vertically over an opening inthe roof deck; a post member telescoped through the sleeve member andextending downwardly through the opening in the roof deck to engage thetank bottom; a pair of tension straps secured at their lower end to 7 rthe sleeve member and secured together at their upper end; a screwmember threadable idly in the top portion of said tension straps; abearing member on the top of said post threadedly receiving the screwmember whereby turning of the screw can lower the post through thesleeve 5 and raise the roof from the tank bottom.

References Cited in the file of this patent UNITED STATES PATENTS MortonIan. 5, Kaplan July 7, Muller May 9, Laird Aug. 15, Perkins June 20,Allen May 29, Orr Feb. 26, Kroll Aug. 5, Wiggins Aug. 12, Sundt Nov. 4,

UNITED STATES PATENT OFFICE CERTIFICATE 0F CORECTION Patent N002,847,755 T August 19, 1958 John F, Mummert et e1o It is herebycertified that error appears in the printed specification of tide abovenumbered patent requiring correction and that the said Letters Patentshould read as corrected below.

Column 3, line 57, for "whenever" read me Wherever column 4, line 10,for "raised" read me raise Signed and sealed this 25th day of November1958a (SEAL) Attest:

KARL He AEQJINE ROBERT C. WATSON Attesting Officer Commissioner ofPatents

